The operating microscope has revolutionized the surgical approach to many neurosurgical diseases by providing magnification, binocular vision and excellent lighting in the depths of surgical wounds, and thus facilitating operative procedures which would otherwise be impossible. These microscope dependent operative procedures occasionally involve microscopic bone dissection and the use of osseous dissection instrumentation. While microsurgical instrumentation has been readily available for work with soft tissue, tumor removal and deep suturing, suitable microsurgical osseous instrumentation is not readily available. The task of microscopic bone dissection has been done with bone dissection instruments which are large and awkward to use. The available bone dissection instruments, commonly referred to as rongeurs, are designed to exert large forces for cutting the hard bone material, which results in the large size of the instrument. Whether the bone dissection task requires the use of the microscope or not, the bite-end, including the punch and footplate of the rongeur must be designed to withstand the forces which a surgeon applies to effect the removal of the bone. However, when performing a microsurgical procedure which requires microsurgical removal of osseous material, it is extremely important that the surgeon have a surgical tool that does not require the surgeon's hand to be in the operating field which may impede visualization through the operating microscope. The known commercially available ronguers are designed for use in non-operating microscope environments, and when used in a microsurgical osseous dissection procedure, the surgeon must cope with the problem. By example, rongeur instruments which are commonly used by surgeons in neurosurgical procedures are available from Ruggles Corp. in North Quincy, Mass. (U.S.A.).
The closest prior art patents concerns the following U.S. patents:
______________________________________ U.S. Pat. No. Inventor Date of Issue ______________________________________ 984,756 P. Frisch Feb. 21, 1911 2,691,370 F.J. Wallace Oct. 12, 1954 2,790,437 W.C. Moore Apr. 30, 1957 4,201,213 P.R. Townsend May 06, 1980 4,574,803 K. Storz Mar. 11, 1986 4,777,948 D.W. Wright Oct. 18, 1988 4,990,148 Worrick, III et al. Feb. 05, 1991 ______________________________________
These patents are of interest for teaching the basic shape of the ronguers and appear to be cumulative of the commercially available surgical instrumentation. The patents also teach improvements in the surgical rongeur instrumentation field, see for example U.S. Pat. No. 4,990,148 to Worrick, III et al., teaching an improved footplate, also termed anvil, for a rongeur. U.S. Pat. No. 2,691,370 is of interest for its teaching of an instrument for use with a telescope as a means to obviate problems associated with visualization of the field of operation in heart surgery. These patents, and known commercially ronguers in the prior art have not addressed the visual obstruction problem encountered by neurosurgeons when using these surgical instruments to perform microsurgical osseous dissections.
Thus, a need is seen to exist for a surgical instrument that has structural feature which assures that a surgeon's hand not be in the operating field, and thus facilitate unimpeded visualization by the surgeon through an operating microscope during a microsurgical osseous dissection procedure. In particular, a need is seen to exist for a rongeur having a shank portion designed with an offset portion (bayonet-like, and hereinafter referred to as offset bayonet portion) that obviates the visual obstruction problem encountered during a microsurgical procedure when using presently commercially available rongeurs.
While the rongeur surgical instrument is the preferred embodiment of the present invention, a need is also seen for other surgical instrument, such as a curette, to embody the same type of offset bayonet portion on a composite shank member of the instrument to obviate visual obstruction problems encountered when using them in a microsurgical procedure.